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In recent years, interest in bio-based polymers has grown tremendously. Such polymers present a lower environmental burden and are attractive alternatives to conventional petroleum-based polymers. Polyglycerol is widely appreciated to be a versatile polymer which could potentially be prepared from renewable resources. Due to the presence of numerous ether groups within the polymer backbone, polyglycerol is sensitive to photochemical oxidation and accordingly the material will not persist in the environment for extended periods. Furthermore, polyglycerol is hydrophilic and biocompatible, in a fashion similar to that of polyethylene glycol. Polyethylene glycol has been employed as a scaffold material for: adhesives, hydrogel wound dressings, and drug conjugation and delivery. Thus, like polyethylene glycol, polyglycerol has numerous potential applications in the pharmaceutical, biomedical, and biotechnological fields. However, unlike polyethylene glycol, polyglycerol possesses a large number of hydroxyl groups which may be chemically modified for different applications.
Despite the tremendous potential of polyglycerol, there is a dearth of synthetic methods which allow for the synthesis of high molecular weight material from inexpensive and non-toxic monomers. For example, while the preparation of high molecular weight hyperbranched polyglycerol has been previously reported, the preparation methods rely on the polymerization of a highly toxic monomer, glycidol. Glycerol, a widely available material produced as a major by-product in biodiesel synthesis, is considerably less toxic and would be an ideal monomer. However, attempts to polymerize glycerol have met with little success, and typically oligomeric glycerol materials (i.e., molecular weights less than 1,000 g/mol) are produced, such as diglycerol, triglycerol, tetraglycerol, and the like. Nevertheless, even oligomeric glycerols have found numerous applications as biodegradable surfactants, lubricants, cosmetics, and food additives.